EnerISS is a software system in which a state-of-the-art urban energy control technology is integrated. This system is ultimately aimed at developing energy-saving, ubiquitous-ecology city, usable in city planning and operating steps. As a branch module of the EnerISS, EnerISS Solution(Modeler/Viewer) was developed to visualize energy distribution, demand and consumption status of a target city. This visualization tool operated by city planers, energy-monitoring engineers, and even consumers is expected to virtually derive an energy conservation and efficient use/supply. First of all, the tool should be able to model space and buildings of the target city in terms of accurate geographic information and to express real-time energy information. One part of the packages, called EnerISS Modeler was therefore developed to build the GIS-based city models in which energy data can be input. The software package contains various user-friendly background functions such as create, open, save, view, navigate, etc. This paper is introducing the development process, theoretical background, and functional explanation for the developed modeling software. One city model was selected as an application example to examine and demonstrate the applicability and efficiency.